Parsing issues with some temporal functions

Using the CQL2 parser with a temporal function having a list of properties as an "interval" value doesn't work.

For example, working with the CQL2 parser I tried a request with this kind of filter, and it failed during parsing:
```
{
"op": "t_contains",
"args": [
{"interval": [{"property": "start_datetime"}, {"property": "end_datetime"}]},
{"interval": ["2000-01-01T00:00:00Z", "2000-01-01T00:00:01Z"]},
]
}
```
This kind of filter corresponds to one of those described here: [https://docs.ogc.org/is/21-065r2/21-065r2.html#_conformance_test_41](https://docs.ogc.org/is/21-065r2/21-065r2.html#_conformance_test_41)
It appears that the parser doesn't expect anything else than string values for the interval arg, while it should also be able to handle a pair of properties.